1. Technical Field
One or more of the embodiments of the present invention relate to an emission control system for removal of regulated combustion components from the exhaust of a combustion process, such as an internal combustion engine.
2. Background Art
A combustion engine exhaust often contains a variety of combustion components or gases including unburned hydrocarbon (HC), carbon monoxide (CO), particulate matter (PM), nitric oxide (NO), and nitrogen dioxide (NO2), with NO and NO2, collectively referred to as nitrogen oxide or NOx.
Conventional emission control systems often use separate devices for the reduction of NOx or particulate matter. For example, a singular SCR (selective catalytic reduction) catalyst is used for converting NOx to nitrogen (N2) and a singular particulate filter (PF) is used for removing particulate matter. In some instances, the singular SCR catalyst and the singular particulate filter are sequentially aligned and disposed separable from each other.
However, conventional emission control systems have met with limited use as they lack, among other things, concurrent and balanced consideration for emission control efficiency and space conservation. For example, the use of multiple SCR catalysts in line with a downstream stand-alone particulate filter can result in substantial space consumption. On the other hand, a singular SCR/PF device, while capable of reducing the space required to some extent, can cause other inherent issues such as inadequate catalyst mixing and/or insufficient catalytic temperature window. For instance, the singular SCR/PF device can result in a relatively narrow catalytic temperature window and/or relatively insufficient catalytic activity at higher temperatures, such as above 500 degrees Celsius.
There is thus a continuing need to provide an emission control system with a relatively high catalytic temperature range and NOx reduction efficiency while minimizing system complexity.